Improvement in pavements



J. H. MGMURRAY 8L S. E. GROSS.

Pavement.

No. 206,812. Patented Aug. 6, 1878.

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UNITED STATES PATENT OFFICE.

JOHN H. MCMURRAY AND SAMUEL E. GROSS, OF CHICAGO, ILLINOIS.

IMPROVEMENT IN PAVEMENTS.

Spccilcntion forming part of Letters Patent No. 206,8l2, lated August 6, IRTS; application tiled January 10, 1878.

To all whom it may concern.-

le it known that we, JOHN H. MCMURRAY and SAMUEL E. Gnoss, of Chicago, in the county of Cook and State of Illinois, h. ve invented a new an d useful Improvement in Pavements, which is fully set forth in the following specification and accompanying drawings, in which- Figure l is a perspective view of one form of our pavement, and Figs. 2 and 3 are longitudinal vertical sections of modifications of the same.

The object of our invention is to furnish a solid and durable pavement 5 and it consists in a layer of small broken stone, upon which is placed a layer of fine stone-screenings or pulverized stone, and on which a superstructure of wooden blocks is placed as a wearing-surface.

Referring to the drawings, A designates in all the figures a layer of small broken stone or m acadam about six inches thick. These broken stone should not be more than two and onehalf inchesin dimension in any direction. B designates in all the iigures a layer of pulverized stone or fine stone-screenings, about two inches thick, and C designates the wooden blocks which form the top layer or wearingsurface, and which may be arranged in different forms. They may be round or split wood blocks, preferably of cypress or cedar wood, set edgewise to the grain, and the interstices filled with gravel and asphalt or cement, as shown in Fig. l, or they may be rectangular wooden blocks set close together in parallel rows across the street, with liquid asphalt or pinetar poured in the joints and crevices, as shown in Fig. 2 5 or they may be rectangular wooden blocks placed in parallel rows across the street, with interstices between each row of about one inch in width, illed with gravel and asphalt, as shown in Fig. 3; but we do not limit ourselves to the form and order of arrangement of the wooden blocks as shown in Figs. 1, 2, and 3.

In the construction of the pavement, the earth should be irst excavated to the proper depth and the usual eonvexity of the road-bed formed. The first layer, consisting of small broken stone, is then laid down and a heavy roller passed over it until it is well compacted,

and upon this thc second layer is placed and also well compacted; or, ifconvenient, after the first layer, consisting of small broken stone, is laid, the road may be opened to travel until it becomes compacted and its surface smoothcned and uniform. In such eases the second layer may be lessened in quantity; or, if the travel should be of sufficient duration and heaviness to pulverize the upper portion of thc layer of broken stone sufficiently to form a surface layer of pulverizcd stone by this fact alone, then any additional material to the layer so formed may be omitted except in illin g any ruts or depressions existing in the surface.

Any of the various kinds or qualities of stone may be used, and if convenient either or both of the layers may be constructed of the stony refuse, scoria, or slag termed furnace slag.7

The wooden blocks are then placed in position by any of the methods best adapted to their different forms.

Ve are aware that water-tight layers of cement and concrete compositions have been placed upon Cobble-stone or rock foundations but we do not claim these. The superior advantages of a layer of ine stone-screenings or pulverized stone is that, while it forms as smooth a bed for the blocks as a layer of ccment or concrete, it is not, like them, impervious, but affords a suflicient and gradual drainage and absorption. It does not uphold and retain in contact with solutions harmful to the texture of the wooden blocks, as does a cement or concrete foundation, but permits them to escape or be absorbed into the earth, thus adding to the durability of the wooden superstructure as well as to the health of the city. At the same time a sufliciently solid foundation is secured, and with enough elasticity to endure all the extremes of temperature and Weather as well as the'burdens of heavy traic without serious impairment, while cement or concrete foundations are very liable to fracture and deterioration from these causes.

Layers of sand or gravel have been used upon a bed of broken stone; but it has been found in practice that sand acts injuriously upon the wooden blocks, and often produces rapid decay, while it is easily displaced or moved by drainage and pressure. Gravel is not well suited for the purposes of a direct foundation for Wooden blocks for many reasons, some of which often depend upon thc particular kind or quality of gravel used; lult the most frequent reason is its want of stability or failure to present and retain in surfacecomposition a uniform and unchanging bed for the blocks.

Another advantage in the use of our upper layer is that a sutiieient quantity of tine stonescreeniugs and pulverized stone 1s usuali y produced at the quarry by the process of crushing or breaking the stone into sizes suitable for the under layer, and which eau be thus readily utilized.

The upper layer of tine stone-screenings and pulverized stone being of the same kind or quality of stone as the under layer, and differing from it only in the size ot' its partit-les, will, under all conditions of temperature and Weather, form with it a more homogeneous foundation than a layer of eement, coni-rete, gravel, sand. or other foreign substanees.

Having thus described our invention, what we elaini as new, and desire to secure by Letters Patent, is-

1. A pavement in which a top layer of wooden blocks is placed upon a foundation consisting of two layers, the lower one of small broken stone and the upper one of pulverizcd stonc or ue stone-screenings, substantially as described, and for the purpose set forth.

2. The combinations of the layers A and B with the Wooden blocks C, the Whole constructed substantially as described, and for the purposes set forth.

In testimony that We claim the foregoing we have hereunto set our hands this 7th day of January, A. l). 1878.

JOHN ll. IVIC/MURRAY. SAMUEL E. GROSS.

\\'itnesses:

E. F. MERRILL, II. E. Wroxv. 

